Photo--assisted current and shot noise in the fractional quantum Hall effect

TL;DR

This paper investigates how AC perturbations influence shot noise in fractional quantum Hall systems, revealing singularities related to quasiparticle charges and proposing photo-assisted transport as a tool for probing these charges.

Contribution

It introduces a non-perturbative refermionization method for analyzing photo-assisted transport at filling factor 1/2, advancing understanding of quasiparticle charge effects.

Findings

Backscattering current and noise show evenly spaced singularities.

Photo-assisted transport can probe effective quasiparticle charges.

Singularities are determined by quasiparticle charge and bias-to-frequency ratio.

Abstract

The effect of an AC perturbation on the shot noise of a fractional quantum Hall fluid is studied both in the weak and the strong backscattering regimes. It is known that the zero-frequency current is linear in the bias voltage, while the noise derivative exhibits steps as a function of bias. In contrast, at Laughlin fractions, the backscattering current and the backscattering noise both exhibit evenly spaced singularities, which are reminiscent of the tunneling density of states singularities for quasiparticles. The spacing is determined by the quasiparticle charge $\nu e$ and the ratio of the DC bias with respect to the drive frequency. Photo--assisted transport can thus be considered as a probe for effective charges at such filling factors, and could be used in the study of more complicated fractions of the Hall effect. A non-perturbative method for studying photo--assisted transport at $\nu=1/2$ is developed, using a refermionization procedure.